Gaza is on the threshold of becoming the first territory to be intentionally reduced to a state of abject destitution, with the knowledge, acquiescence and - some would say - encouragement of the international community. An international community that professes to uphold the inherent dignity of every human being must not allow this to happen.

Across this tiny territory, 25 miles long and no more than 6 miles wide, a deep darkness descended at 8pm on January 21, as the lights went out for each of its 1.5 million Palestinian residents. A new hallmark of Palestinian suffering had been reached.

There have been three turns of the screw on the people of Gaza, triggered in turn by the outcome of elections in January 2006, the assumption by Hamas of de facto control last June, and the Israeli decision in September to declare Gaza a "hostile territory". Each instance has prompted ever tighter restrictions on the movement of people and goods in and out of Gaza. Each turn of the screw inflicts deeper indignity on ordinary Palestinians, breeding more resentment towards the outside world.

Gaza's border closures are without precedent. Palestinians are effectively incarcerated. The overwhelming majority cannot leave or enter Gaza. Without fuel and spare parts, public health conditions are declining steeply as water and sanitation services struggle to function. The electricity supply is sporadic and has been reduced further along with fuel supply in these past days. Unicef reports that the partial functioning of Gaza City's main pumping station is affecting the supply of safe water to some 600,000 Palestinians.

Medication is in short supply, and hospitals are paralysed by power failures and the shortage of fuel for generators. Hospital infrastructure and essential pieces of equipment are breaking down at an alarming rate, with limited possibility of repair or maintenance as spare parts are not available.

It is distressing to see the impact of closures on patients who need to travel outside Gaza to get medical treatment. The demand for such treatment is rising as medical standards fall inside Gaza, yet the permit regime for medical referrals has become more stringent. Many have had their treatment delayed or denied, worsening their medical conditions and causing preventable deaths.

Living standards in Gaza are at levels unacceptable to a world that promotes the elimination of poverty and the observance of human rights as core principles: 35% of Gazans live on less than two dollars a day; unemployment stands at around 50%; and 80% of Gazans receive some form of humanitarian assistance. Concrete is in such short supply that people are unable to make graves for their dead. Hospitals are handing out sheets as funeral shrouds.

As the head of a humanitarian and human development agency for Palestinian refugees, I am deeply concerned by the stark inhumanity of Gaza's closure. I am disturbed by the seeming indifference of much of the world as hundreds and thousands of Palestinians are harshly penalised for acts in which they have no part.

In discharging its mandate, Unrwa delivers a variety of services to improve living conditions and prospects for self-reliance. It is impossible to sustain our operations when the occupying power adopts an "on, off", "here today, gone tomorrow" policy towards Gaza's borders. To take one example, this week we were on the verge of suspending our food distribution programme. The reason was seemingly mundane: plastic bags. Israel blocked entry into Gaza of the plastic bags in which we package our food rations.

In today's Gaza how can we foster a spirit of moderation and compromise among Palestinians, or cultivate a belief in the peaceful resolution of disputes? There are already indications that the severity of the closure is playing into the hands of those who have no desire for peace. We ignore this risk at our peril.

What we should be doing now is nurturing moderation and empowering those who believe that Gaza's rightful future lies in peaceful co-existence with its neighbours. We welcome the new efforts to resuscitate the peace process, revive the Palestinian economy and build institutions. These pillars, on which a solution will be built, are the very ones being eroded.

Yesterday, the people of Gaza received a temporary reprieve when the occupying power allowed fuel and other supplies to enter: 2.2m litres of fuel per week for the Gaza power plant and 0.5m litres a week for industrial usage, hospitals and clinics. We have been informed that the crossings into Gaza will be partially open, allowing Unrwa and other organisations to bring in about 50 trucks a day. No one knows how long the reprieve will last as the resumption of Qassam rocket fire, which we ourselves strongly condemn, will lead to further closures.

The people of Gaza have been spared from reaching new depths of anguish - but only for the moment.

There has never been a more urgent need for the international community to act to restore normality in Gaza. Hungry, unhealthy, angry communities do not make good partners for peace.

· Karen Koning AbuZayd is commissioner general for Unrwa, the United Nations Relief and Works Agency for Palestine Refugees in the Near East www.un.org/unrwa